I am looking for someone with access to plasma or flame spray to test a concept. I recently bought a magnetic induction hot plate [not NuWave - FWIW s/h costs for the second "free" NuWave unit and "free" pots/pans is more than the unit.] and while I have several induction ready pieces of cook ware, I got to wondering why the other items I had could not be adapted.
Some web research indicates the heating mechanism is ohmic heating from eddy currents in the pan rather than hysteresis loss as I had assumed. The reason aluminum and copper pans won't work with normal induction cook tops is that the magnetic field penetrates the material too deeply and the induced current is flowing across too big a conductor cross section with not enough resistance. Some very expensive units use a much higher frequency induction circuit and these will work with aluminum and copper because of the reduced skin depth, but are expensive and in limited distribution. Additionally, pyroceramics/glass-ceramics won't work because eddy currents can't be induced in a non conductor.
Also came across a "stunt" on You Tube where aluminum foil is ignited with a induction cook top. The foil is so thin [1/2 mill] the cross section the induced current flows through is small enough to generate enough heat to melt/ignite it.
My thought is to plasma or flame spray an insulating layer on the bottom of the alumium/copper cook ware, then a thin layer of a conductive material, c. 0.5 mil or possibly thinner, then one or more thicker coats of a protective ceramic over the conductive film. Of course for the glass-ceramics there would be no need for the first insulating layer, just a thin metallic film, and one or more protective layers.
It does not appear that the metallic layer need be magnetic if it is thinner than the skin effect depth so nichrome, molybdenum, etc. may be better than iron, and it may be helpful to provide multiple metallic layers separated by insulating layers on the aluminum/copper cook ware.
The optimum "pattern" for the eddy current layer is unknown, and while a simple uniform surface works well, it may be that the efficiency could be improved by some sort of greek key pattern, radial spokes, closed loops, etc., which should be possible to produce with a stencil or mat, possibly computer cut, when the eddy current layer is applied.
A thin metallic layer on the bottom of the glass-ceramics would prevent their use in microwave ovens, much as you can't use aluminum foil or aluminized packaging, but there may be some configuration that will allow adequate eddy current induction/heating at 20-30 kHz, but will be "invisible" at microwave oven frequencies [c 4.5 gHz]
Any thoughts? This could be a good profit opportunity for someone with flame/plasma spray capability. Feel free to run with the ball. Tons of Corningware / Visions out there. It would be good to see some high tech processes at the cottage industry level?
Below are some of the more interesting sites I came across. The enameled cast iron ware prices will make your socks roll up and down several times? (and can't be used in a microwave)